Without a doubt, the main advantage of this handheld cup vane air flow meter is that it doesn't need to be held exactly in the direction of the wind. Air flow meter with impellers typically have to be held exactly in the direction of the air flow to take accurate measurements. However, this cup vane air flow meter's system is so sensitive that it responds to the smallest of air currents. To perform a correct measurement with the cup vane air flow meter: First turn the meter on, then hold the meter vertically so the cups can rotate until the wind velocity is displayed. In the following picture you can see how to measure wind speed with the cup vane air flow meter.